A heater core, which is located inside a heating, ventilating, and air conditioning (HVAC) module of a motor vehicle supplies thermal energy to the passenger compartment for comfort heating. The heater core is typically a liquid-to-air heat exchanger. A heat transfer liquid, such as a glycol based coolant, conveys waste heat from an internal combustion engine to the heater core where the thermal energy from the heat transfer liquid is transferred to the ambient air flowing through the heater core to the passenger compartment. With the advent of greater efficiency internal combustion engines and hybrid vehicles having smaller internal combustion engines, the amount of thermal energy available to provide comfort to passengers in the passenger compartment may not be adequate.
Exhaust gas heat recovery exchangers (EGHR) are known to be used to capture waste heat from the exhaust gas of an internal combustion engine to supplement the heat provided by the heater core to heat the ambient air directed to the passenger compartment. Aside from providing supplementary heat to the passenger compartment, the heat energy in the exhaust gas can be used to heat other fluids within the vehicle, such as the windshield wiper fluid, motor oil, and transmission fluid.
More efficient and smaller internal combustion engines produce less waste heat in the exhaust gas for the EGHR heat exchanger to recover. Accordingly, there is a need to extract as much waste heat as possible from the exhaust gases of efficient and smaller internal combustion engines to supplement comfort heating and to heat the vehicle fluids as mentioned above.